The speed brake will not flex at all at landing speeds, where the dynamic pressure is low, and I guess that you will not use it at 100% throttle.. unless you are bored with the roo and start
making experiments... in this case, you can reinforce it with a balsa "X" or something like it.

Enrique.

Move the horn up so that the horn connects to the linkage over the center off the hinge line. Most of that play and movement will go away. You will also use a lot less servo throw to get it down.

[quote]ORIGINAL: F86_SABRE

Hi,
a question to the list.
The Roo airbrake has some flexing if pressed backward (simulating air pressure). Airbrake moves around 1/2" - 3/4" backwards.
The Robart type horn (1.25" high type) is situated approximately in the airbrake centre and is connected to the servo by a 4/40 type rod which is about 3" long.
Well a picture says a thousand words so are included.

Should this flexing of the airbake be of any particular concern?


Thanks in advance

Reuben
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Move the horn up so that the horn connects to the linkage over the center off the hinge line. Most of that play and movement will go away. You will also use a lot less servo throw to get it down.
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Kenny has this one pegged.... you are losing your mechanical advantage when the air-brake is fully deployed.

Kenny: I was told that the further out of the hinge line the better since with the horn being further backwards there would be more strength and less backward movement of the airbrake when deployed. I opted for a happy medium...in the centre of the airbrake.

Countryboy: Sorry did not quite understand your expression "has this one pegged".

Enrique: "unless you are bored with the roo and start making experiments" Not correct but let's put it this way it is not quite THE plane I like to fly.

Any further comments on the subject?

With thanks to all for now.

Regards

Reuben

I don't know who told you that but I believe that the opposite is correct. If you put the arm at the outer end of the brake you will run into a problem. If you leave it like it is and look at the linkage while you add pressure to the speed brake you will notice that the servo arm is moving upwards and to the back of the plane before it moves forward towards the servo. Now if you take a horn and place it at the top and move the brake, most of the travel is forward towards the servo. I quarantee if you move the horn your problems will go away.

That means "Has the the correct answer perfect (pegged)".

Thanks for the reply...will adjust...kind regards

Reuben